reducer

reducer.dart

import 'package:equatable/equatable.dart';  
import 'package:flutter/material.dart';  
import 'package:flutter_hooks/flutter_hooks.dart';  
  
class MyFormState extends Equatable {  
  const MyFormState(  
    this.formKey,  
    this.textInputController, [  
    this.dropdown1Value,  
    this.textInput,  
    this.error,  
    this.dropdown2Value,  
  ]);  
  
  final TextEditingController textInputController;  
  final GlobalKey<FormState> formKey;  
  
  final String? dropdown1Value;  
  final String? textInput;  
  final String? error;  
  final String? dropdown2Value;  
  
  bool get isFinished => dropdown1Value != null && textInput != null && dropdown2Value != null;  
  
  MyFormState copyWith({  
    GlobalKey<FormState>? formKey,  
    String? dropdown1Value,  
    String? textInput,  
    String? error,  
    String? dropdown2Value,  
  }) {  
    return MyFormState(  
      formKey ?? this.formKey,  
      textInputController,  
      dropdown1Value ?? this.dropdown1Value,  
      textInput ?? this.textInput,  
      error ?? this.error,  
      dropdown2Value ?? this.dropdown2Value,  
    );  
  }  
  
  @override  
  List<Object?> get props => [formKey, textInputController, dropdown1Value, textInput, error, dropdown2Value];  
}  
  
sealed class MyFormAction {  
  const MyFormAction();  
}  
  
class Dropdown1ChangedAction extends MyFormAction {  
  const Dropdown1ChangedAction(this.value);  
  
  final String value;  
}  
  
class ValidateTextInputAction extends MyFormAction {  
  const ValidateTextInputAction();  
}  
  
class Dropdown2ChangedAction extends MyFormAction {  
  const Dropdown2ChangedAction(this.value);  
  
  final String value;  
}  
  
class ResetAction extends MyFormAction {  
  const ResetAction();  
}  
  
typedef MyFormStore = Store<MyFormState, MyFormAction>;  
  
MyFormState reducer(MyFormState state, MyFormAction action) => switch ((state, action)) {  
      (_, Dropdown1ChangedAction(:final value)) => MyFormState(  
          state.dropdown1Value == null ? state.formKey : GlobalKey(),  
          state.textInputController..clear(),  
          value,  
        ),  
      (MyFormState(textInput: null), ValidateTextInputAction()) => switch (validate(state.textInputController.text)) {  
          null => MyFormState(  
              state.formKey,  
              state.textInputController,  
              state.dropdown1Value,  
              state.textInputController.text,  
            ),  
          final error => state.copyWith(error: error),  
        },  
      (MyFormState(:final textInput?, error: null, dropdown2Value: null), Dropdown2ChangedAction(:final value)) =>  
        state.copyWith(dropdown2Value: value),  
      (_, ResetAction()) => MyFormState(GlobalKey<FormState>(), state.textInputController..clear()),  
      (_, _) => throw Exception('Invalid state/action combination: $state, $action'),  
    };  
  
String? validate(String? value) {  
  if (value == null || value.isEmpty) {  
    return 'Please enter some text';  
  } else if (value.length < 3) {  
    return 'Please enter at least 3 characters';  
  } else if (value.length > 10) {  
    return 'Please enter at most 10 characters';  
  } else {  
    return null;  
  }  
}